NJ Solar Panel System Size and Savings Calculator
Estimate the ideal solar panel system size for your New Jersey home and calculate your projected annual savings, including NJ-specific incentives like the Transition Renewable Energy Certificate (TREC) program and net metering.
Formulas Used
Annual Energy Consumption:
Annual kWh = (Monthly Bill ÷ Electricity Rate) × 12
Required System Size:
System Size (kW) = Annual kWh ÷ (Peak Sun Hours × 365 × System Efficiency Derate)
NJ Peak Sun Hours = 4.21 hrs/day (NREL PVWatts, statewide average)
System Efficiency Derate = 0.80 (inverter losses, wiring, temperature, soiling)
Roof Capacity:
Max Panels = Floor(Roof Area ÷ Area per Panel)
Effective Roof Capacity (kW) = (Max Panels × Panel Wattage ÷ 1000) × Roof Direction Factor × Shading Factor
Annual Energy Production:
Production (kWh) = System Size (kW) × 4.21 × 365 × 0.80 × Roof Direction Factor × Shading Factor
Net Cost:
Net Cost = Gross Cost − Federal ITC (30%) − NJ Sales Tax Exemption (6.625%)
Annual Net Metering Savings:
Savings = Annual Production (kWh) × Electricity Rate ($/kWh)
NJ uses full retail-rate net metering (1:1 credit)
TREC Income:
Annual TREC = (Annual Production ÷ 1,000) × $90/MWh
Total TREC = Annual TREC × 15 years
Simple Payback:
Payback (years) = Net Cost ÷ First-Year Annual Benefit
25-Year Lifetime Savings (with 0.5%/yr degradation):
Lifetime Production = Annual Production × (1 − 0.995²⁵) ÷ (1 − 0.995)
Lifetime Savings = Lifetime Production × Electricity Rate + Total TREC Income
CO₂ Offset:
Annual CO₂ (metric tons) = Annual Production (kWh) × 0.386 lbs/kWh ÷ 2,204.62
Assumptions & References
- NJ Peak Sun Hours: 4.21 hrs/day — NREL PVWatts Calculator, statewide average for fixed-tilt south-facing arrays.
- System Efficiency Derate: 80% — Standard PVWatts default accounting for inverter efficiency (~96%), wiring losses, soiling, shading, and temperature effects.
- NJ Average Electricity Rate: $0.17/kWh — U.S. EIA Electric Power Monthly, NJ residential average (2024).
- Federal Investment Tax Credit (ITC): 30% — Inflation Reduction Act (IRA) of 2022; applies to systems installed 2022–2032.
- NJ Sales Tax Exemption: 6.625% — N.J.S.A. 54:32B-8.55; solar energy equipment is exempt from NJ sales and use tax.
- NJ Property Tax Exemption — N.J.S.A. 54:4-3.113a; added home value from solar is exempt from NJ property tax for 25 years. Added value estimated at $3/W (Lawrence Berkeley National Lab, 2019).
- NJ Net Metering — Full retail-rate net metering (1:1 credit) for systems up to 2 MW under NJ BPU rules (N.J.A.C. 14:8-4).
- TREC Rate: ~$90/MWh — NJ Transition Renewable Energy Certificate program administered by NJ BPU; rate set quarterly. 15-year contract term. Verify current rate at njcleanenergy.com.
- Panel Degradation: 0.5%/year — Industry standard for monocrystalline silicon panels (NREL, 2012).
- CO₂ Emission Factor: 0.386 lbs/kWh — EPA eGRID 2022, RFCE (RFC East) subregion covering NJ.
- Installed Cost: $2.80–$3.20/W — Lawrence Berkeley National Lab "Tracking the Sun" report (2023), NJ residential average.
- This calculator does not account for battery storage, EV charging loads, time-of-use rates, or utility interconnection fees.
- Tax credit eligibility depends on individual tax liability. Consult a qualified tax professional.